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<h2>DESCRIPTION</h2>

<p>
The <b>Graphical Modeler</b> is a <em><a href="wxGUI.html">wxGUI</a></em>
component which allows the user to create, edit, and manage simple and
complex models using an easy-to-use interface.
When performing analytical operations in GRASS GIS, the
operations are not isolated, but part of a chain of operations. Using the
Graphical Modeler, a chain of processes (i.e. GRASS GIS modules)
can be wrapped into one process (i.e. model). Subsequently it is easier to
execute the model later on even with slightly different inputs or parameters.
<br>
Models represent a programming technique used in GRASS GIS to
concatenate single steps together to accomplish a task. It is advantageous
when the user see boxes and ovals that are connected by lines and
represent some tasks rather than seeing lines of coded text. The Graphical
Modeler can be used as a custom tool that automates a process. Created
models can simplify or shorten a task which can be run many times and it can
also be easily shared with others. Important to note is that models cannot
perform specified tasks that one cannot also manually perform with GRASS
GIS. It is recommended to first to develop the process manually, note down
the steps (e.g. by using the <i>Copy</i> button in module dialogs) and later
replicate them in model.

<p>
The Graphical Modeler allows you to:

<ul>
  <li>define data items (raster, vector, 3D raster maps)</li>
  <li>define actions (GRASS commands)</li>
  <li>define relations between data and action items</li>
  <li>define loops (e.g. map series) and conditions (if-else statements)</li>
  <li>define model variables</li>
  <li>parameterize GRASS commands</li>
  <li>define intermediate data</li>
  <li>validate and run model</li>
  <li>save model properties to a file (<i>GRASS Model File|*.gxm</i>)</li>
  <li>export model to Python script</li>
  <li>export model to image file</li>
</ul>

<h3>Main dialog</h3>

The Graphical Modeler can be launched from the Layer Manager menu
<tt>File -&gt; Graphical modeler</tt> or from the main
toolbar <img src="icons/modeler-main.png" alt="icon">. It's also
available as stand-alone module <em>g.gui.gmodeler</em>.

<p>
The main Graphical Modeler menu contains options which enable the user
to fully control the model. Directly under the main menu one can find
toolbar with buttons (see figure below). There are options including
(<font size="2" color="red">1</font>) Create new model,
(<font size="2" color="red">2</font>) Load model from file,
(<font size="2" color="red">3</font>) Save current model to file,
(<font size="2" color="red">4</font>) Export model to image,
(<font size="2" color="red">5</font>) Export model to Python script,
(<font size="2" color="red">6</font>) Add command (GRASS modul) to model,
(<font size="2" color="red">7</font>) Add data to model,
(<font size="2" color="red">8</font>) Manually define relation between
data and commands,
(<font size="2" color="red">9</font>) Add loop/series to model,
(<font size="2" color="red">10</font>) Add comment to model,
(<font size="2" color="red">11</font>) Redraw model canvas,
(<font size="2" color="red">12</font>) Validate model,
(<font size="2" color="red">13</font>) Run model,
(<font size="2" color="red">14</font>) Manage model variables,
(<font size="2" color="red">15</font>) Model settings,
(<font size="2" color="red">16</font>) Show manual,
(<font size="2" color="red">17</font>) Quit Graphical Modeler.

<p>
<center>
<img src="g_gui_gmodeler_toolbar.png">
<br>
<i>Figure: Components of Graphical Modeler menu toolbar.</i>
</center>

<p>
There is also a lower menu bar in the Graphical modeler dialog where one can
manage model items, visualize commands, add or manage model variables,
define default values and descriptions. The Python editor dialog window
allows seeing workflows written in Python code. The rightmost tab of
the bottom menu is automatically triggered when the model is activated and
shows all the steps of running GRASS modeler modules. In case of errors
in the calculation process, it is written at that place.

<center>
<a href="g_gui_gmodeler_lower_toolbar.png"><img src="g_gui_gmodeler_lower_toolbar.png" width="600" height="354"></a>
<br>
<i>Figure: Lower Graphical Modeler menu toolbar.
</i>
</center>

<h3>Components of models</h3>

The workflow is usually established from four types of diagrams. Input and
derived model data are usually represented with oval diagrams. This type of
model elements stores path to specific data on the user's disk. It is
possible to insert vector data, raster data, database tables, etc.
The type of data is clearly distinguishable in the model by its color.
Different model elements are shown in the figures below.

<ul>
  <li> (<font size="2" color="red">A</font>) raster data: <img src="g_gui_gmodeler_raster.png" alt="raster" style="margin: 0px 0px -5px 0px">
  <li> (<font size="2" color="red">B</font>) relation: <img src="g_gui_gmodeler_relation.png" alt="relation" style="margin: 10px 0px 0px 0px">
  <li> (<font size="2" color="red">C</font>) GRASS module: <img src="g_gui_gmodeler_modul.png" alt="module" style="margin: 0px 0px -5px 0px">
  <li> (<font size="2" color="red">D</font>) loop: <img src="g_gui_gmodeler_loop.png" alt="loop" style="margin: 15px 0px -5px 0px">
  <li> (<font size="2" color="red">E</font>) database table: <img src="g_gui_gmodeler_db.png" alt="db" style="margin: 10px 0px -5px 0px">
  <li> (<font size="2" color="red">F</font>) 3D raster data: <img src="g_gui_gmodeler_raster3d.png" alt="raster3D" style="margin: 10px 0px -5px 0px"> 
  <li> (<font size="2" color="red">G</font>) vector data: <img src="g_gui_gmodeler_vector.png" alt="vector" style="margin: 10px 0px -5px 0px">  
  <li> (<font size="2" color="red">H</font>) disabled GRASS module: <img src="g_gui_gmodeler_modulex.png" alt="module" style="margin: 10px 0px -5px 0px"> 
  <li> (<font size="2" color="red">I</font>) comment: <img src="g_gui_gmodeler_comment.png" alt="comment" style="margin: 10px 0px -5px 0px">  
</ul> 

<center>
<a href="g_gui_gmodeler_model_classification.png">
<img src="g_gui_gmodeler_model_classification.png" width="500"></a>
<br>
<i>Figure: A model to perform unsupervised classification using MLC
(<a href="i.maxlik.html">i.maxlik</a>) and SMAP (<a href="i.smap.html">i.smap</a>).
</i>
</center>

<p>
Another example:

<center>
<a href="g_gui_gmodeler_model_usle.png">
<img src="g_gui_gmodeler_model_usle.png" width="600" height="284"></a>
<br>
<i>Figure: A model to perform estimation of average annual soil loss
caused by sheet and rill erosion using The Universal Soil Loss
Equation.</i>
</center>

<p>
Example as part of landslide prediction process:

<center>
<a href="g_gui_gmodeler_model_landslides.png">
<img src="g_gui_gmodeler_model_landslides.png" width="600" height="290"></a>
<br>
<i>Figure: A model to perform creation of parametric maps used by geologists 
to predict landslides in the area of interest.</i>
</center>

<h2>EXAMPLE</h2>

In this example the <tt>zipcodes_wake</tt> vector data and the
<tt>elev_state_500m</tt> raster data from the North Carolina
sample dataset (original <a href="https://grass.osgeo.org/sampledata/north_carolina/nc_rast_geotiff.zip">raster</a> and
<a href="https://grass.osgeo.org/sampledata/north_carolina/nc_shape.zip">vector</a>
data) are used to calculate average elevation for every
zone. The important part of the process is the Graphical Modeler, namely its
possibilities of process automation.

<h3>The workflow shown as a series of commands</h3>

In the command console the procedure looks as follows:

<div class="code"><pre>
# input data import
r.import input=elev_state_500m.tif output=elevation 
v.import input=zipcodes_wake.shp output=zipcodes_wake 
# computation region settings
g.region vector=zipcodes_wake  
# raster statistics (average values), upload to vector map table calculation
v.rast.stats -c map=zipcodes_wake raster=elevation column_prefix=rst method=average 
# univariate statistics on selected table column for zipcode map calculation
v.db.univar map=zipcodes_wake column=rst_average 
# conversion from vector to raster layer (due to result presentation)
v.to.rast input=zipcodes_wake output=zipcodes_avg use=attr attribute_column=rst_average 
# display settings
r.colors -e map=zipcodes_avg color=bgyr                                         
d.mon start=wx0 bgcolor=white                                                   
d.barscale style=arrow_ends color=black bgcolor=white fontsize=10
d.rast map=zipcodes_avg bgcolor=white                                                                                                 
d.vect map=zipcodes_wake type=boundary color=black                                                     
d.northarrow style=1a at=85.0,15.0 color=black fill_color=black width=0 fontsize=10
d.legend raster=zipcodes_avg lines=50 thin=5 labelnum=5 color=black fontsize=10 
</pre></div>

<h3>Defining the workflow in the Graphical Modeler</h3>

To start performing above steps as an automatic process with the Graphical Modeler
press the <img src="icons/modeler-main.png" alt="icon"> icon or
type <em>g.gui.gmodeler</em>. The simplest way of inserting elements
is by adding the complete GRASS command to the Command field in the GRASS command
dialog (see figure below).  With full text search one can do faster
module hunting. Next, the label and the command can be added. In case that only
a module name is inserted, after pressing the <i>Enter</i> button, the
module dialog window is displayed and it is possible to set all of the usual
module options (parameters and flags).

<p> 
<center>
<a href="g_gui_gmodeler_dlg_module.png"><img src="g_gui_gmodeler_dlg_module.png"
width="400"></a>
<br>
<i>Figure: Dialog for adding GRASS commands to model.</i>
</center>

<h3>Managing model parameters</h3>  
All used modules can be parameterized in the model. That causes launching the
dialog with input options for model after the model is run. In this example,
input layers (<tt>zipcodes_wake</tt> vector map and <tt>elev_state_500m</tt> 
raster map) are parameterized. Parameterized elements show their diagram border
slightly thicker than those of unparameterized elements.

<center>
<a href="g_gui_gmodeler_parameter.png">
<img src="g_gui_gmodeler_parameter.png" width="500"></a>
<br>
<i>Figure: Model parameter settings.</i>
</center>

<p>
The final model, the list of all model items, and the Python code window with
<i>Save</i> and <i>Run</i> option are shown in the figures below.

<center>
<a href="g_gui_gmodeler_model_avg.png">
<img src="g_gui_gmodeler_model_avg.png" width="600" height="272"></a>
<br>
<i>Figure: A model to perform average statistics for zipcode zones.</i>
</center>
<br>
<center>
<a href="g_gui_gmodeler_items.png">
<img src="g_gui_gmodeler_items.png" width="600" height="330"></a>
<p>
<a href="g_gui_gmodeler_python.png">
<img src="g_gui_gmodeler_python.png" width="600" height="330"></a>
<br>
<i>Figure: Items with Python editor window.</i>
</center>

<p>
For convenience, this model for the Graphical Modeler is also available for download
<a href="g_gui_gmodeler_zipcodes_avg_elevation.gxm">here</a>.

<p>
The model is run by clicking the <i>Run</i> button
<img src="icons/execute.png" alt="run">. When all inputs are set, the results can
be displayed as shown in the next Figure:

<center>
<a href="g_gui_gmodeler_avg_run.png"><img src="g_gui_gmodeler_avg_run.png" width="500"></a>
<a href="g_gui_gmodeler_avg_map.png"><img src="g_gui_gmodeler_avg_map.png" width="300"></a>
<br>
<i>Figure: Average elevation for ZIP codes using North Carolina sample dataset as 
an automatic calculation performed by Graphical Modeler.</i>
</center>

<h3>Managing model properties</h3>  
When one wants to run model again with the same data or the same names, it is 
necessary to use <tt>--overwrite</tt> option. It will cause maps with identical 
names to be overwritten. Instead of setting it for every 
module separately it is handy to change the Model Property settings globally.
This dialog includes also metadata settings, where model name, model description 
and author(s) of the model can be specified.

<center>
<a href="g_gui_gmodeler_model_properties.png">
<img src="g_gui_gmodeler_model_properties.png" width="350"></a>
<br>
<i>Figure: Model properties.</i>
</center>

<h3>Defining variables</h3>

Another useful trick is the possibility to set variables. Their content can be used 
as a substitute for other items. Value of variables can be values such as 
raster or vector data, integer, float, string value or they may constitute some 
region, mapset, file or direction data type.   

Then it is not
necessary to set any parameters for input data. The dialog with variable settings 
is automatically displayed after model is run. So, instead of model parameters 
(e.g. <tt>r.import</tt> a <tt>v.import</tt>, see the Figure
<em><a href="g_gui_gmodeler_avg_run.png">Run model dialog</a></em> above) 
there are <tt>Variables</tt>.

<center>
<a href="g_gui_gmodeler_variables_run.png">
<img src="g_gui_gmodeler_variables_run.png" width="500"></a>
<br>
<i>Figure: Model with variable inputs.</i>
</center>

<p>
The key point is the usage of <tt>%</tt> before the substituting variable and 
settings in <tt>Variables</tt> dialog. For example, in case of a model variable 
<tt>raster</tt> that points to an input file path and which value is required to be 
used as one of inputs for a particular model, it should be specified in the
<tt>Variables</tt> dialog with its respective name (<tt>raster</tt>), data type,
default value and description. Then it should be set in the module dialog as
input called <tt>%raster</tt>.

<center>
<a href="g_gui_gmodeler_variables.png">
<img src="g_gui_gmodeler_variables.png" width="600" height="330"></a>
<br>
<i>Figure: Example of raster file variable settings.</i>
</center>

<br>
<center>
<a href="g_gui_gmodeler_variables_raster.png">
<img src="g_gui_gmodeler_variables_raster.png" width="600" height="257"></a>
<br>
<i>Figure: Example of raster file variable usage.</i>
</center>

<h3>Saving the model file</h3>
Finally, the model settings can be stored as a GRASS GIS Model file with
<tt>*.gxm</tt> extension. The advantage is that it can be shared as a
reusable workflow that may be run also by other users with different data.

<p>
<!-- TODO: next line, which model? -->
For example, this model can later be used to calculate the average precipitation
for every administrative region in Slovakia using the <tt>precip</tt> raster data from
<a href="https://grass.osgeo.org/sampledata/slovakia3d_grass7.tar.gz">
Slovakia precipitation dataset</a> and administration boundaries of Slovakia from 
<a href="https://www.geoportal.sk/sk/zbgis_smd/na-stiahnutie/">Slovak Geoportal</a>
(only with a few clicks).

<h3>Handling intermediate data</h3>
There can be some data in a model that did not exist before the process and 
that it is not worth it to maintain after the process executes. They can 
be described as being <tt>Intermediate</tt> by single clicking using the right 
mouse button, see figure below. All such data should be deleted following 
model completion. The boundary of intermediate component is dotted line.

<center>
<a href="g_gui_gmodeler_intermediate_data.png">
<img src="g_gui_gmodeler_intermediate_data.png" width="400"></a>
<br>
<i>Figure: Usage and definition of intermediate data in model.</i>
</center>
 
<h3>Using the Python editor</h3>
By using the Python editor in the Graphical Modeler one can add Python code and then 
run it with <i>Run</i> button or just save it as a Python script <tt>*.py</tt>.
The result is shown in the Figure below:

<center>
<a href="g_gui_gmodeler_python_code.png">
<img src="g_gui_gmodeler_python_code.png" width="350"></a>
<a href="g_gui_gmodeler_python_code_result.png">
<img src="g_gui_gmodeler_python_code_result.png" width="350"></a>
<br>
<i>Figure: Python editor in the wxGUI Graphical Modeler.</i>
</center>

<h3>Defining loops</h3>
In the example below the <a href="https://e4ftl01.cr.usgs.gov/MOLT/MOD13Q1.006/">MODIS MOD13Q1</a>
(NDVI) satellite data products are used in a loop. The original data are 
stored as coded integer values that need to be multiplied by the
value <tt>0.0001</tt> to represent real <i>ndvi values</i>. Moreover, GRASS GIS
provides a predefined color table called <tt>ndvi</tt> to represent <i>ndvi data</i>.  
In this case it is not necessary to work with every image separately. 
<br>
The Graphical Modeler is an appropriate tool to 
process data in an effective way using loop and variables (<tt>%map</tt> for a 
particular MODIS image in mapset and <tt>%ndvi</tt> for original data name suffix). 
After the loop component is added to model, it is necessary to define series of maps
with required settings of map type, mapset, etc.

<center>
<a href="g_gui_gmodeler_loop_dlg.png">
<img src="g_gui_gmodeler_loop_dlg.png" width="300"></a>
<br>
<i>Figure: MODIS data representation in GRASS GIS after Graphical Modeler usage.</i>
</center>

<p>
When the model is supplemented by all of modules, these modules should be 
ticked in the boxes of loop dialog. The final model and its results are shown below.

<center>
<a href="g_gui_gmodeler_loop_final.png">
<img src="g_gui_gmodeler_loop_final.png" width="400"></a>
<br>
<i>Figure: Model with loop.</i>
</center>

<p>
<center>
<a href="g_gui_gmodeler_modis_1o.png">
<img src="g_gui_gmodeler_modis_1o.png" width="300"></a>
<a href="g_gui_gmodeler_modis_1.png">
<img src="g_gui_gmodeler_modis_1.png" width="300"></a>
<a href="g_gui_gmodeler_modis_2o.png">
<img src="g_gui_gmodeler_modis_2o.png" width="300"></a><br>
<a href="g_gui_gmodeler_modis_2.png">
<img src="g_gui_gmodeler_modis_2.png" width="300"></a>
<a href="g_gui_gmodeler_modis_3o.png">
<img src="g_gui_gmodeler_modis_3o.png" width="300"></a>
<a href="g_gui_gmodeler_modis_3.png">
<img src="g_gui_gmodeler_modis_3.png" width="300"></a>
<br>
<i>Figure: MODIS data representation in GRASS GIS after Graphical Modeler usage.</i>
</center>

<p>
The steps to enter in the command console of the Graphical Modeler would be as follows:

<!-- TODO: WHY does the white space usage differ?? -->
<div class="code"><pre>
# note that the white space usage differs from the standard command line usage

# rename original image with preselected suffix
g.rename raster = %map,%map.%ndvi
# convert integer values
r.mapcalc expression = %map = %map.%ndvi * 0.0001
# set color table appropriate for nvdi data
r.colors = map = %map color = ndvi
</pre></div>

<h2>SEE ALSO</h2>

<em>
  <a href="wxGUI.html">wxGUI</a><br>
  <a href="wxGUI.components.html">wxGUI components</a>
</em>

<p>
See also selected user models available from this 
<a href="https://github.com/OSGeo/grass-addons/blob/master/grass7/models/">git repository</a>.

<p>
See also
the <a href="https://grasswiki.osgeo.org/wiki/WxGUI_Graphical_Modeler">wiki</a> page
(especially various <a href="https://grasswiki.osgeo.org/wiki/WxGUI_Graphical_Modeler#Video_tutorials">video
tutorials</a>).

<h2>AUTHORS</h2>

Martin Landa, OSGeoREL, Czech Technical University in Prague, Czech Republic<br>
Various manual improvements by Ludmila Furkevicova, Slovak University of Technology in Bratislava, Slovak Republic

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